21533503 has 4 divisors (see below), whose sum is σ = 21746808. Its totient is φ = 21320200.

The previous prime is 21533471. The next prime is 21533507. The reversal of 21533503 is 30533512.

It is a happy number.

21533503 is nontrivially palindromic in base 12.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21533503 - 2⁵ = 21533471 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106501 + ... + 106702.

It is an arithmetic number, because the mean of its divisors is an integer number (5436702).

Almost surely, 2^21533503 is an apocalyptic number.

21533503 is a deficient number, since it is larger than the sum of its proper divisors (213305).

21533503 is a wasteful number, since it uses less digits than its factorization.

21533503 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213304.

The product of its (nonzero) digits is 1350, while the sum is 22.

The square root of 21533503 is about 4640.4205628370. The cubic root of 21533503 is about 278.2092475998.

Subtracting 21533503 from its reverse (30533512), we obtain a palindrome (9000009).

The spelling of 21533503 in words is "twenty-one million, five hundred thirty-three thousand, five hundred three".